Liquid-air cooling system

ABSTRACT

A liquid-air cooling system ( 1 ) has at least one fan device ( 2 ) that consists of at least one variable-speed fan motor ( 3 ) driving a fan impeller ( 4 ) to create a cooling power for a fluid ( 5 ) in a fluid cycle ( 6 ). In order to regulate the speed of the fan motor ( 3 ) by mains of a control and/or regulation device ( 24 ), at least one actual value (t ist ) downstream of the segmented heat exchanger ( 19 ) is compared to a predefined desired value (t soll ), and the control and/or regulation device ( 24 ) adjusts the cooling power according to the current power values of the respective machine unit ( 9 ).

The invention relates to a liquid-air cooling system that includes atleast one fan device comprising at least one variable-speed fan motorthat powers a fan impeller to generate cooling capacity for a fluid of acooling cycle, wherein, in order to control the speed of the fan motorby means of an automatic control system, at least one actual defaultvalue that originates from a machine unit, which can be connected to theliquid-air cooling system, is compared to a desired default value insuch a manner that the cooling capacity of the liquid-air cooling systemis adjusted as a function of the current output values of the respectivemachine unit.

EP 0 968 371 81 discloses and describes a fluid cooling devicecomprising a motor that powers a fan impeller and a fluid pump, whichtakes fluid from an oil reservoir and conveys it into a hydraulicoperating cycle. In the hydraulic operating cycle, the fluid (hydraulicmedium) is heated and routed to a heat exchanger from where the cooledfluid is recirculated to the oil reservoir.

The oil reservoir of the fluid cooling system is configured in the shapeof a basin with particularly high-reaching basin edges that are suitableto form a housing part for receiving the fan impeller and an air-routingchute for a heat exchanger of the fluid cooling device. With the fluidcooling device it is possible to provide an oil reservoir in anespecially compact assembly for storing and circulating large fluidvolumes.

A control system and a method for controlling the speed of a pluralityof fans for cooling a plurality of flow media of a machine unit aredisclosed in DE 100 62 534 A1. The speed of each of the plurality offans is controlled specifically according to an individual heatdissipation requirement of heat transfer cores. For one temperaturesensor, respectively, of each of the plurality of flow media, currenttemperatures are monitored, and wherein each sensor can be operated togenerate a signal that displays the temperature of the respective flowmedium, on the one hand, while it transfers the same, on the other hand,to an electronic control device in order to control the respectivelysingular speed of each of the fans.

Using the previously described solution, temperature-control, especiallycooling, tasks for a fluid of a hydraulic circuit can be basicallyimplemented; however, particularly the temperature of the fluid, whichhas passed through the fan device, is, seen in absolute terms, dependenton the respective and varying ambient temperature of the hydraulic powerpack. The output temperature of the fluid therefore fluctuates in theknown hydraulic power packs and fluid cooling devices after it passesthrough the fan device.

On the basis of this prior art, it is the object of the presentinvention to provide a liquid-air cooling system having a fan devicewith a cooling capacity that takes into account the ambient temperatureof the liquid-air cooling system and that is able to permanentlyimplement an exact desired temperature of the fluid.

This object is achieved by a liquid-air cooling system that has thecharacteristics of claim 1 in its entire scope.

According to claim 1, a liquid-air cooling system is provided thatincludes a fan device with a fan impeller that is powered by avariable-speed fan motor, which basically allows for the implementationof cooling capacity for a fluid in a cooling cycle taking into accountan actual default value—such as a temperature value—that originates froma machine unit that can be connected via the fluid cycle to a liquid-aircooling system. According to the invention, the liquid-air coolingsystem also includes the possibility of taking into account a desireddefault value, wherein the desired default value is compared to theactual default value in such a manner that the cooling capacity of thefan device is adjusted as a function of the actual output values of themachine unit that is supplied with fluid.

An automatic control system handles a corresponding desired/actualcomparison and speed control of the fan motor. The actual default valueand the desired default values therein can be represented by atemperature value. It is also possible to envision that the actualdefault value and the desired default value are described by suitableother characteristic values that relate to a current operating point ofthe machine unit and a current actual temperature value that reflectsthe current operating conditions with regard to the liquid-air coolingsystem.

In an especially preferred embodiment of the liquid-air cooling system,and particularly using memory and processor means of the automaticcontrol system that adjust the speed of the fan impeller, an airtemperature is provided, for example as a desired default value, on theair supply side of the fan device. A desired default value is either atemperature of the ambient air of the hydraulic power pack or atemperature of the machine unit or of a component of the machine unitthat receives a fluid flow-through for the purpose of temperaturecontrol.

Ambient air is provided as a cooling medium to increase the energyefficiency of the liquid-air cooling system, wherein, advantageously,the speed of the fan motor is controlled in such a manner that the fluidtemperature of the coolant is maintained at a value that is lowered, forexample, by 5° Kelvin or more in comparison to a desired temperaturethat represents the desired default temperature. To be able to implementa cost-effective liquid-air cooling system, it is advantageous to selecta variable-speed motor as fan motor. For a fan motor control, it isadvantageous, furthermore, to use a corresponding automatic controlsystem in connection with a machine unit or, when bus systems are used,for the transmission of the desired default value as well as the actualdefault value, or, in the sense of a field bus system, for networking aplurality of machine units. A PID controller therein controls the speedof the fan motor. PID control systems are known to the person skilled inthe art and are commonly used for controlling the operation ofmechanical drives or other mechanical equipment accessories of machineunits. The invention comprises therein any type of PID control. Theoutput quantity of the PID control is limited therein to the maximumallowable speed of the fan motor and/or the fan impeller.

In an especially preferred embodiment, the liquid-air cooling system iscombined onto a compact unit with a minimized required assembly spacecomprising a fluid tank, a motor for powering a fluid pump, the fluidpump itself and the fan motor plus fan impeller and any associatedcooling apparatus as well as a cooler housing. Especially preferably,the motor for powering the fluid pump is mounted directly on the fluidtank.

It is expedient therein to select the geometric dimensions of theaforementioned components of the liquid-air cooling system in such amanner that the fan device and the motor for powering the fluid pumpessentially do not extend beyond a base area of the fluid tank.

The fluid can be, for example, transmission oil or hydraulic oil, oralso a mixture of water and glycol.

With the liquid-air cooling system, it is preferably possible to carryout very exact temperature-control tasks on a machine tool,transmission, extruder, motor, frequency converter or on other types ofmachine units, wherein, using a minimum of energy, it is possible toachieve a permanent, relative to temperature fluctuations or atemperature-controlled machine unit, exact operation of a correspondingmachine unit. Using the liquid-air cooling system, it is also possibleto supply a bed of a machine unit or a singular machine component, suchas a spindle of the machine unit, with fluid, particularly atemperature-control fluid.

The liquid-air cooling system will be described in further detail belowusing an embodied example according to the drawings. Depicted is arepresentation showing the invention in principle and not drawn toscale.

FIG. 1 shows a perspective view of a liquid-air cooling system;

FIG. 2 shows a top view of the liquid-air cooling system in FIG. 1;

FIG. 3 is a schematic circuit diagram of the liquid-air cooling systemaccording to the

FIG. 4 a is an example of the heat output from a machine unit that issupplied to the liquid-air cooling system;

FIG. 4 b shows, in a superimposed curve diagram, the developments overtime of

-   -   the temperature of the fluid before entering in the machine        unit,    -   the temperature of the fluid downstream of the pump outlet,    -   the fluid volume flow V, and    -   the air ambient temperature of the hydraulic power pack;

FIG. 4 c shows, in a superimposed curve diagram, the developments overtime of

-   -   the motor current of the fan motor, measured in Amperes, and    -   the provided motor power of the fan motor, measured in        kilowatts; and

FIG. 4 d shows the development over time of the speed of the fan motor.

FIG. 1 shows a perspective view and partially exploded diagram of aliquid-air cooling system, identified as a whole by the numeral 1, thatsupplies a machine unit 9 and/or a component 11 of a machine unit 9,shown schematically, with a fluid 5, which is envisioned as atemperature-control fluid. Associated with the liquid-air cooling system1 is a fan device 2 that includes a variable-speed fan motor 3 embodiedas an electric motor 12 and that powers a fan impeller 4 with individualfan vanes in the manner of an axial fan. The fan impeller 4 is partiallyreceived by a fan impeller housing 22 and protective grate 17. The fanimpeller housing 22 can be made of plastic or sheet metal parts. As alsoseen in FIG. 2 in a top view of the liquid-air cooling system in FIG. 1,a protective grate 18 is provided in the rear section of the fanimpeller 4 for safety reasons. On the opposite side of the fan impeller4, a heat exchanger 19 in the form of a cellular radiator is disposed inrelation to the protective grate 18. The heat exchanger 19 extendsacross the totality of the projection area swept by the fan impeller 4.

Seen from the perspective in FIG. 1, the fan impeller 4 sucks ambientair from right to left through the ribs of the cellular radiator andtoward the fan motor 3. In principle, the presently shown fan device 2can also be designed and operated with the cooling air in the oppositedirection of flow. The fan impeller housing 22 is designed as a box and,in the present embodiment, it is mounted vertically on a fluid tank 13.The fluid tank 13 is essentially formed as a block-shaped component. Thecross-section of the fluid tank 13 has an L-shape herein, as shown inFIG. 1, such that an assembly base 20 for a motor 15 that is elevatedabove the remainder of the cross-section of the fluid tank 13 is formedfor a motor 15 of a fluid pump 14 that is located inside the fluid tank13. The distributor rail 7 is disposed on the fan housing 22. A sensor28 for detecting the actual temperature t_(ist) is disposed in the fluidconnection of the heat exchanger 19 between the cellular radiator 19 andthe fluid tank 13. The control system 24 is disposed on the motor 3. Thesensor for detecting the desired temperature 10 is disposed, seen in thedirection of flow, upstream of the cellular radiator 19 and protectedagainst direct air flow.

The total fan device 2 and the motor 15 for powering the fluid pump 14extend only negligibly beyond a base area 16 of the fluid tank 13. Thedesired temperature can additionally or alternately also be measureddirectly on the machine unit that is in operation by means of acorresponding sensor.

A motor control unit 24 is mounted directly on the top side of the fanmotor 3, or the outside area thereof provided with cooling ribs,respectively. Resulting is an integrated cable connection between themotor control unit 24 and the fan motor 3. This constitutes a structuralmeasure for avoiding electromagnetic interference fields during theoperation of the fan motor 3 and for increasing the EMV tolerance of thehydraulic power pack 1. The motor control unit 24 includes, inparticular, a frequency converter that is parameterized individually inthe presently shown embodiment by means of a separate operating unit andcan be connected by a cable plug-in connection that is adjustable forthe respective application of the fan motor 3.

The fluid pump 14 conveys a temperature-control fluid in the presentlyshown embodiment, preferably a water-glycol mixture, and is embodied asan immersion pump. The fluid pump 14 therein can basically be designed,in terms of the construction type, more for a large volume flow or morefor a correspondingly high pressure level of fluid 5 in a liquid-aircooling system circuit 6 for the machine unit 9, such that theconstruction type of the fluid pump 14 can be, for example, a rotarypump or a pump with displacement elements like, for example, a rollerpump or a rotary vane-type pump or a gear-type pump. Pump parts of thefluid pump 14 extend from and into the fluid tank 13 for the removal offluid, which are not shown in further detail. In particular, the fluidpump 14 has a pump opening 25 for removing the fluid 5 from the fluidtank 13. After the fluid 5 has run through the machine unit 9 or also acomponent 11 of the machine unit 9, it is routed into the cellularradiator 19 via connection K. Cooled fluid 5 leaves the heat exchanger19 directly via the actual value sensor and pipes 26 in the fluid tank13.

The temperature difference that is adjusted in the present embodimentis >5° Kelvin. A PID controller 27 in the motor control unit 24 servesparticularly as a speed controller for the fan motor 3. The distributorrail 7, the motor control unit 24 as well as the PID controller 27 canalso be combined into an automatic control system (not shown).

FIGS. 4 a to 4 d show logs of relevant operational parameters during theoperation of the liquid-air cooling system 1 and of the machine unit 9that is cooled by the same. For example, FIG. 4 a shows the heat outputthat is supplied by the machine unit 9 to the liquid-air cooling system1 via the fluid 5 heated inside the machine unit 9 over a time intervalfrom 0 to 6000 seconds. The supplied heat output fluctuates during thistime interval between approximately 0.8 to 6.3 kW.

During normal operation (time interval between 1000 seconds and 4,500seconds), the supplied heat output fluctuates in the presently shownembodiment between 2.5 and 6.3 kW.

FIG. 4 b shows relevant temperature developments on the liquid-aircooling system plotted over the same time interval. The top curve inFIG. 4 b shows an embodiment of the temperature development of thetemperature of fluid 5 at the inlet of the liquid-air cooling system 1,meaning after it has left the machine unit 9 and prior to flowing intothe heat exchanger 19. The desired default value as depicted in theembodiment by the mentioned temperature fluctuates therein betweenapproximately 28 and 32° C.

Below the top curve in FIG. 4 b, there is a curve of the fluidtemperature of the fluid 5 after leaving the liquid-air cooling system 1and after the cooling operation. It is immediately visible that theoutput temperature of the fluid 5 almost does not fluctuate at all afteran adjustment process during a time interval of approximately 250 to 600seconds, after which the temperature adjusts itself to approximately27.8° C.

Below these mentioned temperature courses, FIG. 4 b depicts a volumeflow V of the fluid 5 in the liquid-air cooling system 1 during the sametime interval. The volume flow V therein is almost exactly 25 l/min.Below this curve, FIG. 4 b shows a typical course of a desired defaultvalue; presently a temperature t_(soll) the ambient air of theliquid-air cooling system 1 is shown, wherein, during the depicted timeinterval, the ambient air temperature fluctuates between 21 and 23° C.Correspondingly, with the liquid-air cooling system 1, very exacttemperature management of the components 11 of a machine unit 9, forexample in form of a machine tool spindle drive or a total machine unit9, such as a processing center or a machine tool, has become possible.The liquid-air cooling system 1 according to the invention is thereforeable to provide for a marked improvement of the machine's accuracyduring processing.

FIG. 4 c depicts, in the top curve, the course that the motor current ofthe fan motor 3 takes, while the bottom curve represents the course ofthe motor output of the liquid-air system of the fan motor 3. In thedepicted embodiment, the motor current fluctuates between approximately1.2 and 2.2 Ampere, while the recorded motor output is betweenapproximately 0 and 400 Watt.

FIG. 4 d is a representation of the speed fluctuation of the fanimpeller 4 that is necessary to be able to depict the exact outputtemperature of fluid 5, as shown in FIG. 4 b, after exiting the heatexchanger 19. The speed of the fan impeller 4 therein fluctuates in arelatively wide range between approximately 200 and almost 1000revolutions/min. The selected speed and/or speed range is alsodocumented, such that the hydraulic power pack 1 is quite able toensure, owing to comparatively minimal blade tip speeds of the fanblades, a minimal noise level during operation.

1. A liquid-air cooling system that includes at least one fan device (2)comprising at least one variable-speed van motor (3) that powers atleast one fan impeller (4) for generating a cooling capacity for a fluid(5) of a fluid cycle (6), wherein, for the speed control of the fanmotor (3) by means of an automatic control system (24), at least oneactual value (t_(ist)) is compared to a desired default value (t_(soll))in such a manner that the cooling capacity is adjusted as a function ofthe current output values of the respective machine unit (9).
 2. Theliquid-air cooling system according to claim 1, characterized in that anair temperature at a supply side (10) of the fan device (2) is used asthe desired default value (t_(soll)).
 3. The liquid-air cooling systemaccording to claim 1, characterized in that a temperature of the machineunit (9) or of a component (11) of the machine unit (9) is used as thedesired default value (t_(soll)).
 4. The liquid-air cooling systemaccording to claim 1, characterized in that the speed of the fan motor(3) is controlled in such a manner that the air temperature on thesupply side (10) of the fan device (2) is lower than the desired defaultvalue (t_(soll)).
 5. The liquid-air cooling system according to claim 1,characterized in that the fan motor (3) is a variable-speed motor (3)that is triggered by a motor control unit (24) with integrated frequencyconverter circuit with PID controller (27).
 6. The liquid-air coolingsystem according to claim 1, characterized in that the liquid-aircooling system (1) is a compact unit comprising a fluid tank (13), afluid pump (14) with a motor (15) and the fan device (2) with anautomatic control system (24, 27).
 7. The liquid-air cooling systemaccording to claim 1, characterized in that the motor (15) for poweringthe fluid pump(14) and the fan motor (3) with fan impeller (4) ismounted over the housing (24) on the fluid tank (13).
 8. The liquid-aircooling system according to claim 1, characterized in that the fandevice (2) and the motor (15) essentially do not extend beyond a basearea (16) of the fluid tank (13) for powering the fluid pump (14). 9.The liquid-air cooling system according to claim 1, characterized inthat the fluid (5) is a mixture of water and glycol.
 10. The liquid-aircooling system according to claim 1, characterized in that the machineunit (9) that is supplied with fluid (5) by the liquid-air coolingsystem (1) is a machine tool.
 11. The liquid-air cooling systemaccording to claim 1, characterized in that a bed and/or machinecomponent, like a spindle of the machine unit (9), receives the fluid(5) flow-through of the liquid-air cooling system (1).